This project contined for this year at a reduced level of activity. In collaboration with Dr. Judith Christman of the Michigan Cancer Foundation the ability of our synthetic oligodeoxynucleotides to function as substrates for DNA methylases was studied. It was found that differences in substrate properties were related to the position of the modified base dihydro-5-azacytosine. It is expected that conversion of the dihydro-5-azacytosine moiety to the aromatic 5-azacytosine base will change these oligodeoxynucleotides into effective inhibitors of the enzyme. Oxidation of the dihydro-5-azacytosine moiety in these 26-mer oliqodeoxynucleotides continues to be difficult to monitor due to the instability towards alkali shown by both types of oligomers. Assessment of their differences by biological activity might be the only way to monitor the success of the oxidation reaction.